As one pest leaves, Brunswick braces for another's arrival

BRUNSWICK — The bout of cold, wet weather that struck in May may have had a silver lining: it wiped out the area’s burgeoning browntail moth population.

But as one pest disappears from the area, local officials and the Maine Forest Service have teamed up to plan for the arrival of other invasive pests.

Forest Service officials say the 11-day period of rain and cold decimated browntail moth larvae. The caterpillars are notorious for devouring oak leaves, leaving entire sections of forest bare, and also causing rashes and even breathing problems in people.

According to Charlene Donahue, a Maine Forest Service entomologist, the bad weather forced the caterpillars back into their nests, where they became infected with a naturally occurring fungus. She said that while monitoring the outbreak in the Brunswick area recently, she noticed dead caterpillars hanging from their nests with “a halo of fungal spores around them.”

Donahue said the greater Brunswick area was the epicenter of the browntail moth invasion, with more than 7,000 acres of forest affected. Last year’s warm summer combined with milder winter temperatures had Donahue concerned that the moth population was going to explode this summer.

“We were seeing twice as many webs this year than last year and the year before,” she said.

But since May’s cold and wet spell, Donahue said she has received few complaints of human encounters with the caterpillar, and has noticed more leaves on area oak trees.

She predicted that for the Brunswick area, “the browntail moth caterpillar population will be down, and probably down for a number of years.”

But while the moth population recedes, a new pest may be moving in. The emerald ashborer has wreaked havoc on ash trees throughout the Midwest, and Forest Service entomologists believe the pest will have arrived in Maine by 2015.

To prepare for the bug’s arrival, the Forest Service and the town are teaming up to pilot an invasive pest response program called “Planning for the Arrival of Exotic Invasive Pests in Maine’s Urban and Community Forests.” According to Jan Santerre, who coordinates the project for the Forest Service, Brunswick’s response plan will be a model for communities around the state.

Brunswick is the first town in the state to develop a response plan for the emerald ashborer, which can kill a tree in one to three years. Santerre said addressing an emerald ashborer infestation can “completely overwhelm” a municipal budget, due to the high cost of removing multiple trees all at once.

Santerre said the value of having a plan in advance is that a town will have identified which high-priority trees to try to save, and which to cut down early to prevent the insect from spreading. In addition, towns can put dead trees to a more productive use, like donating them to local artists, instead of turning them into wood chips.

As part of the Brunswick pilot program, Forest Service staff have placed emerald ashborer traps in trees around town to see if the pests are already here. The large, purple plastic sheets are tacky on one side and emit the odor of dead ash trees to attract the bugs. The traps have already been placed on the Bowdoin College quad, the Brunswick Mall, and on Water Street near the bike path.

The project is funded by a nearly $49,000 grant from the National Forest Service and a $15,000 grant from the Maine Outdoor Heritage Fund, and will run for 12 to 18 months.